The present system is related to systems for continuously forming elongated monolithic concrete pipe or tunnel within an open excavation.
Continuous monolithic conduit formation began with U.S. Pat. No. 59,578 to Follensbee, who disclosed hinged, collapsible forms used in pouring upright shafts (well casings) in which several of the forms were interconnected coaxially. The bottom form of the interconnected line could be collapsed and withdrawn through the remaining interconnected forms to the top of the pour. There it was reconnected at the top form, completing a cycle of a "leapfrog" effect. Follensbee therefore teaches the basic utilization of several interconnected, coaxial core form sections that can be contracted and moved axially through one another continuously as concrete is being poured to form a continuous elongated monolithic structure. Follensbee described his forms as being used for upright well casing forming purposes. Other systems, following later in the art, have adapted the "leapfrog" system in forming low elongated tunnels and pipes extending along relatively horizontal excavations.
U.S. Pat. No. 515,016 to E. L. Ransome discloses collapsible forms and a truck mechanism for removing a collapsed form axially through the remaining interconnected forms. The method discussed by Ransome includes: (a) moving of the truck to an inner end of the pipe (b) raising an arm of the truck into engagement with the innermost form section, (c) disconnecting the section from the remaining sections, (d) compressing the section to a reduced cross-sectional diameter, and (e) transporting the section to the forward end of the pipe. The section can then be re-expanded on the transporter and reattached to the forward form section, completing a "leapfrog" effect. The Ransome transporter mechanism runs along tracks formed within the individual formed segments. The wheels must therefore be offset from the form removing and replacing mechanism so the transporter can be supported within the assembled line of forms as the transported form is re-expanded and attached to the forward end of the line.
U.S. Pat. No. 1,751,147 to Hackley discusses a method of lining tunnels utilizing the "leapfrog" system of moving successive forms through a plurality of other interconnected, coaxial forms. Hackley makes use of a carriage that is adjustable vertically for the purpose of engaging, stripping and re-expanding forms. The carriage is also used for moving the contracted forms longitudinally within the tunnel being formed. The carriage runs on tracks that are supported by timbers within the excavation.
U.S. Pat. No. 1,788,200 to Molin et al discloses a flexible, collapsible concrete forming tunnel forming core system. An adjustable mechanism is also disclosed that is movable on longitudinal tracks for the purpose of collapsing, expanding and longitudinally moving forms within a tunnel. The truck is movable, along tracks that have been placed on a preformed floor section of the tunnel. The remaining overhead portions of the tunnel are poured later, using partial form sections. The tunnel is therefore formed in two separate steps, first the floor, then the remainder.
U.S. Pat. No. 2,870,518 to Bossner teaches use of hydraulic cylinders and cable arrangements connected between a central structure and a collapsible form for the purpose of expanding and collapsing the hinged form sections.
U.S. Pat. No. 3,022,562 to David C. Card discloses a tunnel form and a carriage for collapsing, transporting and re-expanding forms. This device runs on tracks within the excavation and has various hydraulic arrangements for collapsing, carrying and re-expanding the collapsible form elements. Again, it is noted that the form elements disclosed are formed in several hinged segments and that the carriage runs along tracks that are supported along the bottom of the excavation.
Reissue Pat. No. 26,132 to Cerutti shows another collapsible, hinged form member with a truck arrangement adapted to collapse and re-expand the form members and to move them longitudinally within the formed pipe or tunnel. The carriage or truck here is suspended from a track system that is carried above the floor surface of the tunnel.
U.S. Pat. No. 3,123,883 to James H. Peirsol describes collapsible upper core form members separable from tunnel floor form member. The upper core form member, includes a cam mechanism for expanding the form to a desired semi-circular cross-sectional configuration. Wheels are provided on the floor form members to allow longitudinal movement of the upper arcuate core form sections.
U.S. Pat. No. 3,768,267 to Chlumecky discloses a system by which tunnels are lined with interconnected lining and support structures. These structures are placed within the tunnel in a contracted configuration and transported longitudinally through previously expanded forms to an inner end. There they are re-expanded and connected to the previously joined supports. A rail network is provided to support the form section transport carriage.
None of the above referenced patents disclose a system by which an enlarged, horizontal conduit or tunnel can be formed literally continuously along an elongated open excavation for an extended period of time, primarily because the individual form sections will eventually become crusted over with hardened concrete and will lock into place within the tunnel. The form sections must therefore be periodically removed for cleaning and reapplication of form release prior to reuse. This substantially slows the operation and requires use of additional equipment and workers above the excavation. Further difficulty is encountered with providing as separate units an excavation trimming device, an inner form section mechanism and the slipforms themselves. Perfect coaxial alignment of the individual interconnected forms is difficult to maintain with these elements operating independently of one another.
It therefore becomes desirable to obtain some form of system utilizing the advantages of the leapfrog method of forming tunnels and pipes whereby the pour may be extended continuously and simultaneously with the leapfrog operation, trimming of the excavation, and cleaning of the form sections. It is also desirable to obtain such a system in which the form transporter is supported by the interconnected, static line of forms and will move longitudinally therein on pneumatic tires, therefore avoiding the use of rails.